Field of the Invention
The present invention relates to a medical image processing technique for processing a radiograph of an inside of a body of a patient and a radiotherapy apparatus using the same.
Description of the Related Art
In radiotherapy performed as a treatment by emitting radiation to an affected part of the patient, the affected part may change over time with respiration, heart beats, motions of intestines and internal gas, and the like in some cases. In such a case, the motion of the affected part is tracked to determine proper timing of emission of radiation, or radiation is emitted while the affected part is traced.
To track such a changeable affected part, a tracking scheme is known in which the affected part is tracked based on an X-ray radiograph showing the periphery of the affected part.
This scheme has a problem that a bone reflected in the radiograph lowers detection accuracy of a tracking target. To cope with this problem, a medical image processing technique is considered to be useful. The medical image processing technique generates, from an X-ray radiograph, a radiograph showing only bone and/or a radiograph with the bone removed. For example, in Patent Document 1 (U.S. Pat. No. 7,545,965), a radiograph is used to generate a radiograph showing only the bone. The radiograph showing only the bone is subtracted from the original radiograph to generate a radiograph without the bone.
However, the scheme of Patent Document 1 needs prior learning using a pair of radiographs as teacher images, the pair of radiographs being a radiograph and a radiograph showing only the bone, which are acquired in advance with a dual-energy X-ray imaging apparatus.
It is concerned that the scheme using the teacher images may cause deterioration in performance of medical image processing in the case where radiography conditions are different between the teacher images and a processing target image. Furthermore, there is a problem that a person who is an object of the teacher images is contaminated by radioactivity.
Note that the radiograph includes the meaning of radiographic image, fluoroscopic image and digitally reconstructed radiograph (DRR).